Puberty too soon

Last Updated: Saturday 04 July 2015

MANY girls in the us are starting puberty
far earlier than is widely considered
normal, according to a recently published report of the first large-scale,
multi-racial study conducted by Marcia
E Herman-Giddens, professor of maternal and child health at the Chapel Hill
School of Public Health, University of
North Carolina. Nearly half of the
African -Arnerican and 15 per cent of
Caucasians girls studied, reached puberty
and began developing sexually by the
age of eight (Paediatrics, Vol 99, No 4).

This study involved over 17,000 girls
in the age-group of three to 12 years,
who were seen in 65 paediatric clinics all
over the us. About 1,600 of the girls, or
9.6 per cent, were African-American. At
the age of eight years, 48.3 per cent of
the African-American girls and 14.7 per
cent of the Caucasian girls began developing breasts or pubic hair or both.
Menstruation started at 12.16 years in
the African -American girls on an average and at 12.88 years for Caucasian
girls. The average age of menstruation
has remained almost unchanged for over 45 years.

This study challenges the textbook
timetable of puberty, based on decades
old research on British girls. Existing
medical guidelines have it that it is
abnormal for girls to show the first
signs of puberty before the age of
eight. As this study shows that a large
percentage of American girls have
one or both of these characteristics at seven years of age, and in
some cases by three years, either
the textbooks are outmoded or
there are some other, unknown
factors. The early onset of
puberty was noticed in both
the Caucasian and the African-American girls, although there
racial differences.
were some
On an average, the African
American girls showed the
first signs of sexual maturity
about a year earlier than the
Caucasian girls.

To understand the implications of these observations, it is
important to elaborate on the
role of the hormone oestrogen in
the human body, particularly in
early puberty. Oestrogen is a
powerful chemical with its
receptors in about 300 different
human tissues from the brain to
bone to the liver. Its levels begin
to rise at the age of about eight.
The hypothalamus plays an
important part as it spurs the
pituitary gland to release hormones, which in turn prompt
the ovaries to produce oestrogen. By the age of 11 or 12 years.
production of oestrogen and
other hormones begins to trigger the
development of breasts, growth of the
underarm and pubic hair, and the
beginning of menstruation.

In addition, these hormones also
trigger adolescent features such as oilier
hair and blemished skin. In fact oestrogen starts its functions in the pre-natal
state. It helps in the formation of the
foetus's brain during its early stages of
development. It also affects learning
ability and memory through later life.
Scientists are not very clear as to how
oestrogen works in the brain, but its role
clearly goes beyond menstruation.

Herman-Giddens and her team
wanted to find out whether 'environmental oestrogens', chemicals that
mimic oestrogen, are bringing about the
early puberty noticed in the American
girls. Such a relationship between environmental contamination and sexual
abnormality, was noticed in the early
80s by scientists working on alligators.
While studying as to how many alligators from Florida's Lake Apopka could
be hunted without making the population crash, it was noticed that many of
the males had become nearly sterile.
Subsequent research showed that thousands of gallons Of DDT-containing pesticide was responsible. This started the
study of gender-bending characteristics of pesticides.

Subsequently it was also confirmed
that hundreds of chemicals of the postwar age resemble the human sex hormone oestrogen. These include polychlorinated biphenyles, used in the
manufacture of electronics, pesticides
such as endosulfan and atrazine, polycarbonate plastic found in many baby
bottles and water jugs and chlorine
compounds that bleach paper. Their
molecular structure resembles that of
oestrogen, so they influence the same
receptors in the body that are sensitive
to oestrogen, as the receptors cannot
distinguish them. Consequently, the
,oestrogen mimics' can trick the body
into turning off, or boosting certain bio-chemical pathways, especially in the
reproductive system, disturbing normal
development in both sexes.

Though the role of oestrogen
like pollutants in diseases like breast
cancer and emdometriosis, the painful
inflammation of the uterine lining that
often causes infertility, has been investigated, there are still no confirmed studies to show that the pollutants can
actually switch on the same biological
pathways as real oestrogen. Abnormalities in males due to oestrogen mimics, including testicular malformations
at birth, have been reported in several
countries.

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